The present invention concerns focussing systems for still or motion-picture photographic cameras of the type employed to automatically adjust the camera's state of focus, or else to indicate to the user the direction in which the state of focus is to be adjusted by him, in dependence upon an automatically performed state-of-focus evaluation or subject-distance measurement involving the emission of radiant energy from the camera to the subject, its reflection back towards the camera, and its reception at the camera by a transducer system operative for generating an electrical signal from which focus control information is derived.